Viscose modifiers



United SMCS Pate'ffi tiene Melvin AdajxiDietrich, Claymontnpell, assignorhtofE I.

P onti deNemofqF Companys. Wilmlgtn Del" a corporation of Delaware l k *l N Dawingf. Applicatidn May 29, 19er," Serial N0. 228,975

21 Claims. (CL' 18-54) a calcllatedf,

led the gel swelling Yratio of the primary la Se. andfto hek improve# are selltllssef articles by ring the manufacturing of object..islttolprovidex t .1. f l alldexamplesw-the Vcaustic content-of 6.55%-erefersv to -the PropertletYet ahfuhmef emA .f total alkalinity-expressed."aslhsodiumhydroxidew `It` in-- new rou e 0 a 1g 9m-195% g y atlgue cludes the free sodium hydroxide and that combined rgnera'd-CHUIQSG-bfhaYmg-.nonTenulaied Surf-- in the form of sodiumH` carbonate sodium trithiocarf3.9@ .and Wlh g-lves high tenaclty m twisted me cord bonate and sodium cellulose Xanthate.

diameter -into al"primarycagltigland` regenerating' bath,- comprising 9.5% H2504,` r 1337i NazSOn-an'd -v10%n Z11SO4 ,`l Theyarn--islgivenll bath travelpf-41" by using-- a' roller guide: The( apparatus and ge'neraI procedure us'e'df to extrude' isc`ose-i`nto-the' bathlandlto collect ytheb h formelduryarn are essentially ithmsmews" those-used comat mef'cially in -th'egso-calle'd bobbrn or spoolspinning proc--- ess.4 he specie conditions includefa bath temperatureof 62"'\C. ndar'stfeedfwheelgfspeedfof480 inches per minu The' lame'ntsfar'eca md throughY a-2% acidV bath'fa't98'9 -CI-by-a second'ffe'dlwhe'el'rotating lati such a speed as to givewl'QOfZ: stretch beyond the-first feed wheel. After stretchingl-the yarn is held at constant length, either by multiple wraps about the secondfeed-.Iwheellorz between the second and a third feed wheel, in such a manner that the yarn retains its stretched length for 50 to 100inches,v before collection" at relativelyv low tension on a tbobbin. -The resulting;sregnelatedf gelyarn is washed free of acid and saltl and-then proc# eSlSefd The'tyjdms are. slashed whlewatatd twisted 3 turns per .inch andtestedafter conditioningl n.176? jF. andA 56% |relative humidity for 48,hour,s., Se ofthe slashed Yamiti's also plied t9.a..prdptnllQQ/Zsdnstruction, two strands of the1100.denier. .yann beingjcombined to, make the,l cord. 'g1`he cords ar,ethen tested after being Cnditoned nlla fashionsimilailtlathefyarlil;\,.

The properties oftheyarnand cord from/th 4.,scose described herein. vare d listed. in .Table I.. togetheryrfor comparison with those of unri ened, unmodied viscose.

These o b`je'cts aref accomplished by adding'ft kIViscose.' preferably at least about.0,.05% ,of .a soluble. t-of an 1ST-substituteddithidcarbamic acid aridA eyrudfng' h,the resultant viscose into' anacid)coagulating,bathjcontaining 40 about 1%,t0labout 15%.,zinc. sulfate, d stretchingthe resultant filaments, preferably in a-secondarly l BSisoluble-sa'lt of an N-srubstitutedditliibcarba` is meant salt of an lN-sub's'titut'e'dvdithiocarbam dissolves in 6%l aqueous sodi'umfhydroxide" to the 45 extent of atglest 0.05%'. @For this Hfil-i .'l' y l,

ers should have no rad'ical'hving more than 1 8 carbon atoms; thosev containing 5a.y having nmorev are Vtoo insoluble. The preferred substituted dithilaili more'thr 10"crbo`ii at l of vscos'erayoriy'riil" f Gel swellmgs were deteruined'iin both yarn spun and lmscast-A from the-various vlscoses. The numerical valuesmof gelmSWCllng given below for various yarn 65 QPlmPPOYCmEHS Xanthat'eA-crumbsarre dissolved inla solution of caustic- The acidity of the spinning bath is an important factor in determining the gel swelling and resultant yarn and cord properties from any viscose, and modified viscoses generally require different acidities than do unmodified viscoses to obtain maximum properties. Selection of optimum acidity, of course, is a matter of simple experimentation for one skilled in the art. Spinning the unmodified, unripened viscoses at the acidities used for unripened, modified viscoses does not lead to the improved properties attained by the process of this invention.

The yarn produced by this and other examples has a number of properties which distinguishes it sharply from other regenerated cellulose yarn. The most readily apparent modifications are the unsual cross-section and surface features. For yarns prepared from unmodified viscose spun into a zinc bath, a skin or outer shell which swells to a different extent in water than that of the core is visible. These yarn cross sections show both deep and shallow crenulations around the contour of the fila ment. However, for yarns spun into zine baths from viscose modified with the dithiocarbamate modifiers of this invention, the skin area is much greater, the boundary between the skin and core is very diffuse and the yarn has no appreciable crenulations so that the yarn has a relatively smooth surface. Such yarns are described also in the Cox patents, U. S. 2,536,014, 2,535,044 and 2,535,045, issued on December 26, 1950, on applications filed December 14, 1946, April 26, 1947, and April 26, 1947, respectively.

The fact that the filaments of the invention have smooth surface and considerably lower secondary swelling (water take-up by dried yarns) results in more resistance to fibrillating, laundering, and fatiguing than exhibited by normal crenulated viscose yarns.

Example II A 5-6.5 viscose (5% cotton linters cellulose- 6.5% total sodium hydroxide) modified with 0.25% sodium amyl dithiocarbamate is prepared and spun in the manner described in Example I, using a 10.5% sulfuric acid, 17.0% sodium sulfate, Zinc sulfate coagulating and regenerating bath. The yarns are washed, slashed, and some of the yarn was plied to a cord of 1100/2 construction. Yarn and cord properties are given in Table Il, along with those for a regular Viscose control. It will be noted that the yarn from the modified, unripened viscose shows large improvements in cord strength and fatigue resistance of the cord over yarn produced from unripened, unmodified viscose spun under similar condi- TABLE In Unripcnecl, Unripened,

unmodified modified Bath Acid, Percent 8. 2 8. 5 Yarn Properties:

Tenacity, g./d., dry 4. 66 4. 77 Tenacity, gld., wet 3.15 3. 33 Tenacity, gld., loop 3. 51 3. 88 Elongation, percent, dry. 9. 8 12. 9 Elongation, percent, Wet. 17. 6 25. 1 Elongation, percent, loop 7. 5 10. 3 Gel Swelling (yam) 2. 79 2. 13 Gel Swelling Ratio (l 1.0 0.38 Cord Properties:

Tenacity, gld., conditioned 3. 66 4. 10 Tenacity, g./d., oven-dry 4.12 4. 39 Fatigue, minutes 119 349 Example IV A 5-6.5 viscose (5% cotton linters cellulose- 6.5% total sodium hydroxide) modified with 0.06% sodium hexamethylene bis (dithiocarbamate) is prepared and spun in the manner described in Example I, using a 9.5% sulfuric acid, 17.0% sodium sulfate, 10.0% zinc sulfate ccagulating and regenerating bath. The yarns are washed, slashed, and part of slashed yarn was plied to a cord of 1100/2 construction. Yarn and cord properties are given in Table IV, along with those for a regular viscose control. It will be noted that the yarn from the modified, unripened viscose shows large improvements in cord strength and fatigue resistance of the cord over yarn produced from unripened unmodified viscose spun under similar conditions, even though the dry yarn tenacity of the modified item is actually lower than that of the control. This may be attributed, in part, to the greatly improved elongatlons.

TABLE IV Unripened, Unripened, unmodified modified Bath Acid, percent 8.2 9. 5 Yarn Properties:

Tenacity, g./d., dry 4. 66 4. 05 Tenacity, g./d., \vet 3.15 3. 26 Tenacity, g./d., loop 3. 51 3. 40 Elongation, percent, dry. 9. 8 13.7 Elongation, percent, wet. 17. 20. 1 Elongation, percent, loop 7. 5 11.8 Gel Swelling (yarn) 2. 79 1.97 Gel Swelling Ratio (lm) 1.0 0.33 Cord Properties:

Tenacity, g./d., conditioned 3.66 3.84 Tenacity, g./d., oven-dry... 4. l2 4. 24 Fatigue, minutes 119 445 Example V A 5-6.5 viscose (5% cotton linters cellulose-6.5% total sodium hydroxide) modified with 0.3% potassium pentamethylene dithiocarbamate is prepared and spun in the manner described in Example I, using an 8.5% sulfuric acid, 17.0% sodium sulfate, 10.0% zinc sulfate coagulating and regenerating bath. The yarns are washed, slashed, and part of the yarn plied to a cord of 1100/2 construction. Yarn and cord properties are given in Table V, along with those for a regular viscose control. It will be noted that the yarn from the modified, unripened viscose shows a large improvement in cord Example III A 5-6.5 viscose (5% cotton linters cellulose- 6.5% total sodium hydroxide) modified with 0.16% sodium butyl monoethanol dithiocarbamate is prepared and spun in the manner described in Example I, using an 8.5% sulfuric acid, 17.0% sodium sulfate, 10% zinc sulfate coagulating and regenerating bath. The yarns are washed, slashed, and a part of the slashed yarn plied to a cord of 1100/2 construction. Yarn and cord properties are given in Table III, along with those for a regular viscose control. lt will be noted that the yarn from the modified, unripened viscose shows large improvements in cord strength and fatigue resistance of the cord over yarn produced from unripened unmodified viscose spun under similar conditions.

' strength over-cords from yarn produced from unripened unmodified vlscose spun under simllar conditions.

TABLE V Unripened, Unripened, unmodified modified Bath acid, percent 8.2 8. 5 Yarn Properties:

Tenacity, g./d., dry 4. 66 4. 62 Tenacity, g./d., wet 3.15 3. 25 Tenaclty, g./d., loop 3. 51 3. 52 Elongation, percent, dry 9. 8 13. 5 Elongation, percent, wet 17. 6 26. 4 Elongation, percent, loop 7. 5 10. 4 Gell Swelling (yarn) 2. 79 2, 20 Gel Swelling Ratio (film) 1.0 0.71 Cord Properties:

Tenacity, g./d., conditioned 3. 66 4.03 Tenacity, g./d., ovendry 4.12 4. 48

It has been demonstrated in the foregoing examples that the dithiocarbamate modifiers markedly reduce gel swellmgs and that the reduction in gel swelling is accomi l spniedinbynnoasesimcyarmiand cordfipropertes. ":fIn L particular, ithas been shown that the modied'yarns ibiwlitlnrlowq gel lswel'lingpgive.- `ammich'higher:flconverslonl of strenfgtluz-toacordfstrengthfthan :do: yarnstfromznn- :y

.rphenoxyeihanoi, umethoity-ein@infettiariel, :ibutonythcxyaethanolpplrenoxyethoxyethanoltetraethylene glycoluiiepreparedbfromcfmodiiim viscoses. '1 Ten 5-6l5 f viscoses are .-.pmparedtaasninelxamplei Icand modified .with 'fthe tiagentsishowri in; Table. 'VI. l sfEilmsf vare'fcast lfrom .fthe vis- :Jfcose'tin theimanner:describedA previously.` and. `gel V'swelling improved yarnsfor'otherliregenerated'cellulbsestructures ,'Insome cases, a tcombinati'oniof `three for' more modifiers 1 suchy as illustrated 1 'by :Examplef VI thati follows i mayi-be :cratiosiaresde'terminedrxIn? this case the :coagulatingbath -l5 fincorporat'edfsinraithe'f viscose-land' spuniwithdrexcel-lnt the zahle.

v f rTArBLB l A 'Ge 1Swel ModifyingrAgent ling Ratio '(Films) ,Nonew f. 7.1.00 i 0.58%sodinmmetliyl dithi'ocarbamate 0. 81 0*.24%i*s0d.iumibenzyl dithiacarbamnte 0.151 0.2L%sodium ethylene .bis (dithiocarbamate) I 0,;61 fil. u sodium.`l',3;cyc1ohexan bis'. (dithiocarbamate) 0 30: 0.46% sodium-idibutyldithiocarbamaten 0 49 0.22% sodium dimethyl dithiocarbamate. 0.`57 Y 0.21% sodiumdioctyl dithiocarbamate 0.76 A0.22% sodium lauryl'dithiocarbanate 0.94 0143%'lithium cyclohexyl'dithiocarbamate 0;'81 -0.'9%r;sodinnr adithiocarbamates of` theffollowing mixture: .:10%..hexndecy1; .r1 0%.. octadecy1;..r35% .octadecenyk .-45%

' .'octdecdienyl' 0.'4 84 ..In :addition"*tothezalready named dithiocarhamates thcre aremanyothers 'that'.cantfbeused. Included among lthese- -additional'modifiersware sodiumhexamethylene 4bis bbutyldithiocarbamate); sodium 'ethylenebis (methyl idit'hiocrbamate.) ,-"sdium 1,4=cyclohex ane1bis (ethyl. di- '5tl1iocarbam`ate); sodium xylylene bis (dithiocarbamate), adfthe'elike.

5.252 about 4.9 .gi/

Iresults.

' Example VI tents (higher salt indices) cant-:be usedinfthewviscose l' when l the dithiocarbamatesfi described 1 herein-i vare"added andthere appears tobean vadvantage 'ins'tret'chfaljility land level ofyarnl'propertiesfif salt 4.indices hifgherithan While the majoritybfnthe .fc-item mdiers; haVe.b.een .45 5 are used. It -is necessary 'to use 30%"or greater amounts Tltutd Ldithix'ycarbamic' acids containing no 'more than 10 y'carbon-.atoms -in anyA I'radicaland .in whichl the lnitrogen "isf-attached" to1A aliphatic'carbon. n

-YThe 'di-thiocarbamate modifiers 'f for effective results "lfeasteiaboutf. 0.05% and,"A in general, it s lunnecessary i to eusefmore'fthan 0575'% of agent, a'generally luseful range beingabout 0.05 to 0.3% by weight of viscose. [The "optimun'f concentra'tionlofvv anygiven 'agent depends 'on its fffetivenessg. on itsmolecular-weight, -and'on its stability. G0

'dior-exam`ple,' largericoncentrations of sodium dibutyl "lithiocarbamate a1' e-neededV than for sodium hexameth- 'ylenebis'-(dithiocarbamate). Italso depends to some `.fextenteonjprocess variables such as the spin ning speed, d slsinceat-highfspinningspeeds used in industrlal practice, 60

less agent is desired ithanlat' lower speeds, for the reason that-'the IVrate1oineutraliza`tion of the filament should be feta'.r`ddffonly"to"the extent compatible with complete coagulation duning-'the'short'time the filament is in con-l Bt'acttrwth the'fcoagulating bath. Determination of 'thev 70 optimum concentratiomoffthe dithiocarbamate compound is a matter of simple experimentation'for'those skilled nin'tthe'fart.

the modifier may be added tothe '-causticuse'dzin: con- 75 m'tcrting the fxan'thatefcrumbs iitolviscose for `.to `already .pceparedrviscose ".It:. is.'obvious"from this thatthe controlled vweights of modicrfcould..alsoi'beadded -tofthe cellulosic components being converted into viscose such as the celluloseala-lkali;cellulose..onxanthatecrumbs.

The dithiocarbamate m'diiers may'be us'ed alone or in admixture wvit-hcentain'f'ther: compounds which augment` the modification action and which in themselves .smay'bemodiers Such compounds include .al'number of carbon ldisulde -to obtainsalt indices bf` 5 -or-'over .'in unrip'ened viscoses.

While the use of unripened viscose is of --spcialinvvte'rest' l in i the@ process 1of this invention, vit! f'can' bef shown that considerable improvements iin. `gel swelling are4 also fobtainedf-with normallyripenedfviscose; thusffdem'o'nstrat- V'ing that the-'p'rocess is directly-applicable'to=existing y"plantpractice, #For example,l a'7'6 visco'selcontaining 32% CS21 and 0.25`%2sodiurn` 'cyclohex'yl dithiocarbarnate is prepared. 1In'this .caselhowe'verg the viscose isr'ipened las is done for -lnormal' viscose'.to 1saltf'index"fofff4.5

(xanthate sulfur-1.05%). FiImsae-'castfrom' thefv'is'- cose in the 'mannerf described previously" fand K.gel swellings are determined. \In 'lthis 'lease thecoagulatingf bath'lfis 8.9-17-10 (H2SO4-Na`zSO4-'-ZnS`4-). AThe@gele:swellinglso obtained is` 88%y of thatfl an accompanying control from unmodiiiedf viscose.

The spinning baths suitable 'forusein 'theiln" entin "contain 'sulfuric'.acidi and-zinc sulfate. Zinc slf'ate "an essential componenti 'of 'thel spinning Abathl since, inlits absence, lthe dithiocarbamate compounds havefno'- effect on spinningl and'- yarn properties. Sodium"v slfateis us- `uallypres'ent1but is not essential. flf desiredfadditional salts fdivalent-m'etals knownlto reinforce'lor supplement the'action of 'zinc sulfate-may be'uSQd, Suchasferrus sulfate, manganese sulfate, onn'i'ckel sulfate, particularly .the `rst-nam-edfsalt. .Theuse'cf Vthese 4divalentmetal salts makes it "possible to use. smaller "amounts" of ,zinc sulfate than are necessary in their absence. Preferably,` the .spinning bath contains -from 4% to 12% of su'lfuric acid, from 13% to 25% of sodium sulfate, and from' 1% to 15% of Zinc sulfate, optionally with 1% to about 5% ,ferrous sulfate. The optimumY quantity of zinc sulfate `from the standpoint of practical spinning speeds; reducztion.ingel swelling, and extent of modification of physical properties of yarn appears -to be 3% to 10%. The Iforegoing examples have demonstrated" the markedlre- 'duction in, gel swellingcaused by the"spin`ning'of 5='-6.5 .viscoses containing; dithiocarbamat'es into l0 "zn'c" sulmodified with 0.21% sodium cyclohexyl dithiocarbamate, will give a gel swelling only 57% of that from an accompanying control from unmodified viscose when both are cast in an 8.5% H2SO4-22% Na2SOfi-5% ZnSO4 bath. With the addition of dithiocarbamates to viscose, it is possible to obtain excellent yarns in the upper range of bath acidity under which conditions normal unmodified viscoses give yarns of decreased quality. The temperature range of best spinnability is from 40 C. to 75 C. On the basis of available data, it is desirable to have the bath acidity as low as is practical for a given spinning speed in order to get optimum filament structure and yarn properties. Each of the above concentrations should be adjusted to each other and to the composition of the viscose. lt is desirable to use as high a total solids content as possible in the coagulating bath to give the highest degree of gel shrinkage and improved stretchability.

The filaments may be given a long travel of 130 to 250 inches in the primary bath by means of a multiple roller setup which gradually applies tension to the traveling filaments and thereby Orients them while they are still plastic. The preferred method, however, is to apply a part or all of the stretch beyond the primary bath in a secondary bath or to use a combination of air and hot bath stretch. The secondary bath may consist simply of water or of dilute (1% to 3%) sulfuric acid, or it may have the same composition as the coagulating bath but at a greater dilution, e. g., one-fourth of the concentration of the coagulating bath. The thread can be given a travel of to 50 inches in the secondary bath of hot water or dilute bath. The temperature of the secondary bath is preferably between 50 C. and 100 C. Stretches of 80% to 100% are preferred for producing high tenacity yarn and to 30% for textile type yarns. When using the two-bath spinning system, the preferred procedure is to draw off the freshly coagulated gel yarn with a feed wheel speed equal to or less than the jet velocity and to apply all of the stretch between positivly driven rollers traveling at different speeds. The amount of stretch applied depends on the properties desired for the yarn. The bobbin process has been used in the example, but it is immaterial whether spinning is by bobbin, bucket, or continuous processes. The yarn cake is washed free of acid and salt and then dried under tension. lf preferred, it may be twisteror Slasher-dried to enable the dry elongation of the finished product to be controlled.

Spinning may be carried out with the aid of spinning tubes such as described in Millhiser U. S. Patent 2,440,057 or Drisch et al. U. S. Patent 2,511,699. These tubes of relatively small diameter and of substantial length confine the bath and filaments in their critical stage of formation so that no substantial tension is imposed on the filaments because the speed of concurrent bath ow is y maintained only slightly below the speed of the filament bundle passing through the tube. It is thus possible to materially increase the rate of spinning over methods earlier described without substantially sacrificing the desirable properties set forth above.

The novel and improved yarns obtainable through the process of this invention can, in general, be used instead of regular regenerated cellulose fibers for any purpose where the latter are finding applications, more particularly in the textile and tire cord industries. The production of yarns having smooth (non-crenulated) surfaces is highly advantageous, for such yarns have very high strength and improved soil and abrasion resistance. The combination of high tenacity and high fatigue resistance represents a material advance and a new type of regenerated cellulose article.

Any departure frorn the above description which conforms to the present invention is intended to be included within the scope of the claims.

I claim:

1. A process for the production of regenerated cellulose articles which comprises adding to viscose a soluble salt of an N-substituted dithiocarbamic acid and extruding the resultant viscose into an acid coagulating bath containing about 1% to about 15 sinc sulfate.

2. A process in accordance with claim l in which said dithiocarbamate is sodium cyclohexyl dithiocarbamate.

3. A process in accordance with claim l in which said dithiocarbamate is sodium amyl dithiocarbamate.

4. A process in accordance with claim 1 in which said dithiocarbamate is sodium butyl monoethanol dithiocarbamate.

5. A process in accordance with claim 1 in which said dithiocarbamate is sodium hexamethylene bis (dithiocarbamate).

6. A process in accordance with claim 1 in which said dithiocarbamate is sodium benzyl dithiocarbamate.

7. A process in accordance with claim l wherein the amount of zinc sulfate is from about 3% to about 10%.

8. A process in accordance with claim 1 in which the said acid bath contains about 4% to about 12% sulfuric acid and about 13% to about 25% sodium sulfate.

9. A process in accordance with claim 1 in which the said acid bath contains about 4% to about 12% sulfuric acid, about 13% to about 25%'sodium sulfate and about 1% to about 5% ferrous sulfate.

10. A process for the production of regenerated cellulose articles which comprises adding to viscose a soluble salt of an N-substituted dithiocarbamic acid containing no radical containing more than 18 carbon atoms and extruding the resultant viscose'into an acid coagulating bath containing about 1% to about 15% zinc sulfate.

1l. A process in accordance with claim 8 in which the said dithiocarbamic acid contains no radical having more than 10 carbon atoms.

12. A process for the production of regenerated cellulose articles which comprises adding to viscose up to about 0.5% of a soluble salt of an N-substituted dithiocarbamic acid and extruding the resultant viscose into an acid coagulating bath containing about 1% to about 15% Zinc sulfate.

,13. A process for the production of regenerated cellulose articles vwhich comprises adding to viscose up to about 0.5% of a soluble salt of an N-substituted dithiocarbamic acid and regenerating the resultant viscose by extruding it into an acid bath containing about 1% to about 15% Zinc sulfate, thereby reducing the gel swelling ratio of the resultant gel structure to less than 1.0.

14. A process for the production of regenerated cellulose structures which comprises extruding into an acid coagulating bath viscose containing a measured amount of a salt of an N-substituted dithiocarbamic acid which salt is soluble in 6% aqueous sodium hydroxide to the extent of at least about 0.05%, said bath containing about 1% to about 15% zinc sulfate.

15. A process for the production of regenerated cellulose articles wliich comprises adding to viscose an alkalimetal salt of an N-substituted dithiocarbamic acid and extruding the resultant viscose into an acid coagulating bath containing about 1% to about 15% zinc sulfate.

16. A process for the production of regenerated cellulose articles which comprises adding to viscose about 0.05% to about 0.5% of a soluble salt of an N-substituted dithiocarbamic acid; extruding the resultant viscose into an acid coagulating bath containing about 1% to about 15% Zinc sulfate; and stretching the resultant formed article about 20% to about 100% during spinning.

17. A process for the production of regenerated cellulose articles which comprises adding to viscose about 0.05% to about 0.5% of a soluble salt of an N-substituted dithiocarbamic acid and extruding `the resultant viscose into an acid coagulating bath maintained at 40 C. to C; which contains about 4% to about 12% sulfuric acid, about 13% to about 25% sodium sulfate and about 3% to about 10% zinc sulfate.

18. A process in accordance with claim 1 wherein said N-substituted dithiocarbamic acid contains a cyclohexyl group attached to said nitrogen (Ng) atom.

19. A process in accordance with claim 1 wherein said N-substituted dithiocarbamic acid is a mono-N- substituted dithiocarbamic acid.

20. A process in accordance with claim 1 wherein said N-substituted dithiocarbamic acid is' a di-N-substituted dithiocarbamic acid.

2l. A process in accordance with claim 20 wherein said disubstituted dithiocarbamic acid contains a methyl group attached to the nitrogen atom.

References Cited in the file of this patent UNITED STATES PATENTS Number 

1. A PROCESS FOR THE PRODUCTION OF REGENERATED CELLULOSE ARTICLES WHICH COMPRISES ADDING TO VISCOSE A SOLUBLE SALT OF AN N-SUBSTITUTED DITHIOCARBAMIC ACID AND EXTRUDING THE RESULTANT VISCOSE INTO AN ACID COAGULATING BATH CONTAINING ABOUT 1% TO ABOUT 15% ZINC SULFATE. 